Assuming you know the rules for Object Serialization, my aim in this article is to write an app in J# which does Object Serialization and then I shall decipher the serialized data.
Below is the app which does the object serialization. This app is inspired from :
// Demonstrates Object Serialization
import java.io.*;
import java.util.*;
class Store implements Serializable {
private int n;
public Store(int n) { this.n = n; }
public String toString() { return Integer.toString(n); }
}
public class link implements Serializable {
private static int next_int = 0;
private Store[] d = {
new Store(next_int++),
new Store(next_int++),
new Store(next_int++)
};
private link next;
private char c;
// Value of i == number of segments
public link(int i, char x) {
c = x;
if(--i > 0)
next = new link(i, (char)(x + 1));
}
public link() {}
public static void main(String[] args) throws ClassNotFoundException, IOException {
link w = new link(4, 'a');
ObjectOutputStream out = new ObjectOutputStream(
new FileOutputStream("link.out"));
out.writeObject(w);
out.close();
}
Now using the app from my previous post, when I try to read the contents of the output file link.out, I get the following result:
>file_bytes.exe link.out
ac ed 0 5 73 72 0 4 6c 69 6e 6b c8 f1 6d e 38 aa 2f ca 2 0 3 43 0 1 63 5b 0 1 64 74 0 8 5b 4c 53 74 6f 72 65 3b 4c 0 4 6e 65 78 74 74 0 6 4c 6c 69 6e 6b 3b 78 70 0 61 75 72 0 8 5b 4c 53 74 6f 72 65 3b 29 20 b6 39 0 37 55 a0 2 0 0 78 70 0 0 0 3 73 72 0 5 53 74 6f 72 65 ee f5 85 2f 82 b5 ab 5a 2 0 1 49 0 1 6e 78 70 0 0 0 0 73 71 0 7e 0 6 0 0 0 1 73 71 0 7e 0 6 0 0 0 2 73 71 0 7e 0 0 0 62 75 71 0 7e 0 4 0 0 0 3 73 71 0 7e 0 6 0 0 0 3 73 71 0 7e 0 6 0 0 0 4 73 71 0 7e 0 6 0 0 0 5 73 71 0 7e 0 0 0 63 75 71 0 7e 0 4 0 0 0 3 73 71 0 7e 0 6 0 0 0 6 73 71 0 7e 0 6 0 0 0 7 73 71 0 7e 0 6 0 0 0 8 73 71 0 7e 0 0 0 64 75 71 0 7e 0 4 0 0 0 3 73 71 0 7e 0 6 0 0 0 9 73 71 0 7e 0 6 0 0 0 a 73 71 0 7e 0 6 0 0 0 b 70
Total no of bytes read :286
Now, let us decipher this data. I would use “à” as a notation for “implies”
ac ed à STREAM MAGIC
0 5 à STREAM VERSION
73 à Terminal constant for OBJECT
72 à Terminal constant for CLASSDESC
0 4 à length of the class name (“link”)
6c 69 6e 6b à ‘l’ ‘i’ ‘n’ ‘k’
c8 f1 6d e 38 aa 2f ca à serialVersionUID
2 à serializable flag
0 3 à No of serializable fields in class “link”
43 à ‘C’ , primitive type code for Char
0 1 à length of the char field name i.e 1 here
63 à ‘c’ , name of the char field
5b à ‘[‘ , object type code for array
0 1 à length of the array field name i.e 1 here
64 à ‘d’ , name of the array field
74 à Terminal constant for STRING
0 8 à Length of type name is 8
5b 4c 53 74 6f 72 65 3b à ‘[‘ ‘L’ ‘S’ ‘t’ ‘o’ ‘r’ ‘e’ ‘;’ (field descriptor format)
4c à ‘L’ , object type code for object
0 4 à length of the object field name i.e 4 here
6e 65 78 74 à ‘n’ ‘e’ ‘x’ ‘t’
74 à Terminal constant for STRING
0 6 à Length of type name is 6
4c 6c 69 6e 6b 3b à ‘L’ ‘l’ ‘i’ ‘n’ ‘k’ ‘;’ (field descriptor format)
78 à Terminal constant for ENDBLOCKDATA
70 à Terminal constant for NULL (null reference for super class)
0 61 à char value is ‘a’
75 à Terminal constant for ARRAY
72 à Terminal constant for CLASSDESC
0 8 à Length of type name is 8
5b 4c 53 74 6f 72 65 3b à ‘[‘ ‘L’ ‘S’ ‘t’ ‘o’ ‘r’ ‘e’ ‘;’ (field descriptor format)
29 20 b6 39 0 37 55 a0 à serialVersionUID
2 à serializable flag
0 0 à No of serializable fields in the array class
78 à Terminal constant for ENDBLOCKDATA
70 à Terminal constant for NULL (null reference for super class)
0 0 0 3 à No of fields in the array
73 à Terminal constant for OBJECT
72 à Terminal constant for CLASSDESC
0 5 à String length of “Store”
53 74 6f 72 65 à ‘S’ ‘t’ ‘o’ ‘r’ ‘e’
ee f5 85 2f 82 b5 ab 5a à serialVersionUID
2 à serializable flag for Store class
0 1 à No of serializable fields in Store class
49 à ‘I’ , primitive type code for integer
0 1 à length of the char field name i.e 1 here
6e à ‘n’ , name of the char field in Store class
78 à Terminal constant for ENDBLOCKDATA
70 à Terminal constant for NULL (null reference for super class)
0 0 0 0 à int value of the field ‘n’ ( which is 0 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 1 à int value of the field ‘n’ ( which is 1 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 2 à int value of the field ‘n’ ( which is 2 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 0 à handle to the link class
0 62 à char value is ‘b’
75 à Terminal constant for ARRAY
71 à Terminal constant for REFERENCE
0 7e 0 4 à handle to the array class
0 0 0 3 à No of fields in the array
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 3 à int value of the field ‘n’ ( which is 3 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 4 à int value of the field ‘n’ ( which is 4 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 5 à int value of the field ‘n’ ( which is 5 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 0 à handle to the link class
0 63 à char value is ‘c’
75 à Terminal constant for ARRAY
71 à Terminal constant for REFERENCE
0 7e 0 4 à handle to the array class
0 0 0 3 à No of fields in the array
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 6 à int value of the field ‘n’ ( which is 6 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 7 à int value of the field ‘n’ ( which is 7 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 8 à int value of the field ‘n’ ( which is 8 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 0 à handle to the link class
0 64 à char value is ‘d’
75 à Terminal constant for ARRAY
71 à Terminal constant for REFERENCE
0 7e 0 4 à handle to the array class
0 0 0 3 à No of fields in the array
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 9 à int value of the field ‘n’ ( which is 9 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 a à int value of the field ‘n’ ( which is 10 here )
73 à Terminal constant for OBJECT
71 à Terminal constant for REFERENCE
0 7e 0 6 à handle to the Store class
0 0 0 b à int value of the field ‘n’ ( which is 11 here )
70 à Terminal constant for NULL ( for the “next” member of this link object)